What is the primary respiratory concern for divers?

Pulmonary Overpressure Injury, also known as Barotrauma is the number one respiratory concern because of its seriousness.  Because of this lung condition several more serious issues can arise such as traumatic arterial gas embolism, Pneumothorax, and mediastinal emphysema.  With the gas embolism, air is forced into the arterial circulation that obstructs blood flow to the brain, leading to permanent brain damage unless treated quickly through recompression.  To prevent Pulmonary Overpressure Injury, a diver would need to be free from chronic pulmonary disease, Pneumothorax, and asthma, meaning the disease is inactive.